Cushioned tire



H. C. LORD CUSHIONED TIRE Dec. 9, 1952 7 Sheets-Sheet 1 Filed May 9, 1949 Srmentor Dec. 9, 3952 H. c. LORD 2,620,345

CUSHIONED TIRE Filed May 9, 1949 '7 Sheets-Sheet 2 Hu 4 c 5411 INVENTOR ATTORNEY Dec. 9, 1952 H. c. LORD 9 03 CUSHIONED TIRE Filed May 9, 1949 7 Sheets-Sheet 3 H. C. LORD CUSHIONED TIRE ea. 9, W52

7 Sheets-Sheet 4 Filed May 9, 1949 H. C. LORD CUSHIONED TIRE Dec. 9, 1952 7 Sheets-Sheet 5 Filed May 9, 1949 IIII'I'I'I' I I attorney Dec. 9, 1952 H. c. LORD 2,620,845

CUSHIONED TIRE Filed May 9, 1949 7 Sheets-Sheet 7 lrwentor Gltorneg Patented Dec. 9, 1952 CUSHION ED TIRE Hugh 0. Lord, Erie, Pa., assignor to Lord Manu facturing Company, Erie, Pa., a corporation of Pennsylvania Application May 9, 1949, Serial No. 92,152

10 Claims.

This invention is a cushion tire in which the tread is connected to the rim through a cushion free to yield preferably locally. One feature of the cushion is that it has inclined walls carrying the load in shear. In a preferred form the cushion walls are a circumferential lattice section, that is, a section formed of circumferentially extending walls intersecting to form a lattice in radial transverse section. Such a form of lattice makes possible various forms of lattice dimensions differing in relative resistance in various directions, namely, as circumferentially under traction, radially under load and laterally under side strain. In a preferred form the circumferential lattice walls are spiralled to provide a helical lattice. The helical lattice section makes possible utilizing the rotative movement of the lattice walls relative to the air to produce a heat absorbing, wiping action of air against the wall surfaces. The wiping action is aided by the retarding effect of the inertia of the air which increases the relative wiping action between the air and the lattice wall surfaces. The helical lattice is also, in some instances, easier to mold since the complete. tire may be unthreaded from helical cores. The tread may have spiral road engaging ribs which have a squeegee action for driving traction and braking. Further objects and advantages appear in the specification and claims.

In the accompanying drawings, Fig. 1 is a radial transverse section on line I-l, Fig. 2, through a tire having a circumferential lattice between the tread and rim and formed with axially separated side portions; Fig. 2 is a diagrammatic view showing the manufacture of the tire by wrapping an extruded section around the rim; Figs. 3 and 4 illustrate a tire of circumferential lattice formation adapted to manufacture in a mold having segmental cores; Fig. 5 is a radial cross section through a modification with the segmental cores in place; Fig. 6 is a section through the Fig. 5 tire mounted on a wheel rim; Fig. 7 is a side view of a helical lattice tire; Fig. 8 in a section on line 8-8 of Fig. 7; Fig. 9 is a section on line 9-9 of Fig. '7 slightly modified with respect to the central, cooling, air slot; Fig. 10 is a fragmentary developed, circumferential section through a helical lattice; Fig. 11 is a transverse section through a helical lattice tire omitting the central, cooling, air slot; Fig. 12 is a transverse section through another helical lattice tire omitting the central, cooling, air slot, the tire being formed in axial halves with the lattices on the meeting faces in register to continue the spiral passages; Fig. 13 is a plan view of the tread of the Fig. 12 tire; Fig. 14 is a fragmentary side view of one of the helical lattice sections, Figs. l5, l6, and 17 are sections on lines l5|5, l6--l5 and l'I-I'l of Fig. 14; and Fig. 18 is a cross section of one of the helical lattice sections.

Referring to the drawings, l indicates the tread, 2 indicates a demountable rim having side flanges 3 with rolled edges 4, and 5 indicates a circumferential lattice section bonded to the rim and connecting the tread section and rim. The lattice section wall is formed with triangular circumferential cores 6 and 1 respectively, adjacent the tread and rim, and intermediate diamond circumferential passages 8. The triangular and diamond sections have sharp corners 9 at the sides where the load tends to squeeze the corners together and rounded corners I!) at the top and bottom where the load tends to spread the corners apart. The load is transmitted from the tread through inclined walls ll, I2, l3 and [4 to junctions l5, I6, and I1 and from these junctions through incIined wallsl8, I9, 20 and 2! to junctions 22 and 23 adjacent the side flanges 3 of the rim. The junctions l5 and I1 project laterally beyond the tread to provide side cushions. The lower ends of the walls l8 and 2! are thickened at 18a, 21a to seat on the outwardly curled edges 4. This prevents localized strain at the bond to the rim.

The radial load transmitted through the inclined lattice Walls lI-M and l8-2l is subjected to shear stresses. For the angle shown the greater part of the load is transmitted in shear and is effective in cushioning the load. Rubber in shear gives a more satisfactory cushioning performance than rubber in compression. The distribution of the load between compression and shear may be varied by the inclination and span of the lattice walls. Circumferential load due to the driving torque and the braking forces is transmitted circumferentially along the lattice walls thus bringing the extended walls circumferentially under shear stress. The resistance to these forces is substantially unaffected by the inclination of the lattice walls. Because these forces are circumferential the forces are resisted by a greater length of the lattice walls than is called into action to withstand the local radial loads ordinarily resulting from contact of the tread with the road. The greater resistance to circumferential load such as that due to driving traction and braking forces is a desirable characteristic.

In Fig. 2 is shown an extruding head 24 which extrudes a section 25 having the radial cross section of the tire shown in Fig. 1. This extruded section is cut along a bias as indicated at 26, wrapped around the rim 2 and then cured in a mold.

Fig. 3 illustrates the manufacture of the tire that may be formed with segmental'inwardly retractable cores. The triangular sections 6 and 1 are formed by cores 21' and 28 and the diamond sections 8 are formed by cores 29. The rim is made in split sections 30 which after moulding are spread apart to permit withdrawal of the cores. After withdrawing the cores 28, the cores 29 are withdrawn through 'core' openings3l 'in the junctions 22 and 23. After removal of the cores 29 the cores 2'! may be removed through the core opening 32 in the junction IS. The specific construction of the cores 2?,"28, 26, and of the core extensions in the openings 31 and 32 'arenot illustrated. In'the' use of the tire-the split 1'im=-'sections"3 5 are squeezed together sufli- 'cient to'close the core-openings 3| and 32. Thereafter the -tire functions as -thoug-h molded 'with- ""out the sepa'rations. If desired, the mating surfaces *of the core openings 3I- and 32-may be coated with cement so as to insure-against slip- '-page. The'angular or'stepped shape of the core -epmngs- 3 l and 32 te'nds to "prevent slippage. The apex of each an'gular opening 3 l' points -=along the inating inclindwall. Theforces at -the joint forined-byopenings 32'are substantially wholly-horizontal and in the direction to close the' opening.

*In FigfiA is shown another arrangement for 'inakin'g the'-tire" c' f Fig l th rough the u'se of segmental retractable e'oi es. In this a-rrangenie'nt the rim is split into foursections, angular -='inner --se'ctions 33 on -the iriner corner of junctions 22- and 23gand angular'outer sections on the outer sections 34 'of the outer corners of' the junctions. The rim s'ections34 'have outwardly -'-'curved edges' 35--corresponding 'tothe-edges 4 on the rim 2. 'jThe' triangular section! is formed -by a segmentaleore 5 35. The diamond sections 13 are formed by segmental cores 38 which are removd-through' radial eore openings 39 through the' een ter of junc tiens 22-and 23. The-outer 1 triangular section 6 is-'- formed 1 bya segmental i core 49 removed through -radial' eore openings 4! thro'iigh the' center ofthe junctions 15. As in the Fig- '3 construction, thesegmental core iorriiing the tr-i'angularsection- 1 is'removed first.

Itis then possible to spread the" rim sections 33 and 34- siifficieht to remove the cores 38,- and thereafter the co're 4D. In the use er the tire the rim sections 33 aiid 34 are"squeezed'-=tog ether summer-1c to close -the'core -op'enin'gs 39 jand I 4 I There 'is P substantially-notendency' for slippage -at the' 'opening" 4 l'- since the" forces transmitted-- from the t'rad are ho'r-iaohtaland in the direc- 'tion 'to' closethewperiing. The sa'me is -true of -=the openings 39. :snppage'at-these openings -is further preventedhy the bonding of 3 the junchens" 22 and 23 tothe -r-im- -sections 33 and 3 34.

1 In the modification 's'ho\vn in"Figs. 5 and 6 there is arr-arched-out'er span 42 havinga convex "center section 43 which 3 progressively flattens under a l'oadtd increase the' widthf tread contact. The sides-of the-convex center' section-43 merge 'into inclined shear sections; which are inclined at'such an angle that radial load-is trans- -'mittedpredominately-in shear. There is-no sharp line of demarcatiori'between the endof the tread,

" l -comprising channel sections 61- clamped together section 43 and the beginning of the shearsection 4 44. Under load the width of tread contact continually increases and thereby shortening the length of the shear sections. This produces a desirable stiffening of the tire under shock loads. The load from the shear section 44 is transmitted to split rims 45 through inclined shear sections 45 which are bonded to the inclined surfaces *4! of the rim Sections and extend laterally outwardfrom the rim section in substantially direct 0 continuation of the surfaces 41. The inclination of the section 43 is such that radial loads "'aresubstantially wholly accommodated in shear. The sections 45 and 44 meet at junctions 4B, havingsharp corners on the inside which tends to reduce localized stress at junction, as the sections 44 and 45 are brought together under radial loads. The junctions'48 project beyond the rims 45 and serve as side cushions for the tire. Because of 'the'angle of the shear sections 44 and 46, side thrusts on the junctions 48 are transmitted substantially wholly in direct stress (compression or tension).

The load'carrying capacity'of the construction so far describedmay'be 'furtherincreased through 5 the use of supplemental load carrying sections 49,

59,-5I, and 52. These supplemental sections'together with' the span" 42 and sections-46, form a circumferential lattice similar to that shown in Fig.1. The sections' 49'and50 extend from sharp 'corners'53 and 54 on theunderside of the section *43 toward"jiinction 55. The sections 5| and 52 extend from sharp corners 56 and 51 on the junc- 1 tions'-55' toward stepped joints- 58' and the rubber overlying the ri'm45. Theinclination of the sections"-49-"-52 is such that radial loadsare transm'itted priinarily in shear. It will be'noted that --the tread span 45 resting on the two'side lattices 'tends to' yield fajster than the two side supports 44, 45, 49'52-on the side lattices. If, therefore, the -load is sufii cientto' completely flatten the tread-portion 43, additional load encounters increasing resistance, being the resultant ofthe two supporting lattices.

preferred 1 form of the" segmental, inwardly, r'etr'actable cores-isillustratedin- Fig. 5. The under -orinner "side ofthe sections 5i and 52 is formed" by radially split cores 59, each having aradial section 60 p'rojecting through the space 'b'et'ween the split'rims'45. The'upper' or outer surfaces of sections 5| and 52 and the under: or lower surfaces ofthe 's'ections49 and 50 are formed bysegmental cores 6 l each having a 'section 62 l extending through the joint 58 and along' the -under surface 'of the core"- 59 and the outer surface of-the coresection 50. The adjac'ent surfaces of the 's'ections 44 and 46 are formed'by segmental cores' 63, each having a "section154"extending through the joints 58 -be- 'n'eath the core section62 and down along the outersurfaces of the'core sections 62. The un- I dersidewf' the convex section 43 and the-upper or outerside of sections-49- and50 are formed by' radially split segmental cores"65,' each -having a radial core section 13 6- extending through 65 -the center of the junctlon"55 and between the 66). The removal of the cores is effected seuentian as described above, cores 59 being "removed first and being followed by' the removal "of cores63j6 I, and-55.

The tire is-mountd throu'gh theme of a spacer by bolts 68. The channel sections have flanges 69 engaging the underside of the split rim section 45, and flanges 78 engaging a wheel rim 1|. Upon tightening of the bolts 68 the rims 45 are brought together sufiicient to close the openings formed by the cores 68, 62, 64, and 86. Thereafter the tire functions as though molded without the stepped separations since the forces on the sections 4952 are in the direction to close the core openings.

In Figs.'7l1 is shown a tire in which the circumferential lattice section spirals at constant pitch along the axis of the tire to provide a helical lattice. Since the pitch of the helical lattice is short compared to the pad of the tread in contact with the road, the load and thrust resisting characteristics of the tire are substantially the same as the circumferential lattice tire. The construction distributes the gravity loads, the side loads, and the circumferential braking and traction stresses so that the accumulation of stresses'at local points is largely avoided.

The helical lattice tire is preferably made in two symmetrical halves, right and left, which are placed together to form the tire as shown in Figs. 8 and 9. Each of the halves has a tread section 12, a helical lattice section 13 secured to rim section 14. The rim sections have downwardly curled edges 15 for attachment toa wheel rim. Such wheel rims and the engagement of the curled edge are standard. The tread sections butt at the center along a line 16. The rim sections are spaced apart at the center to provide a slot 1'! for the flow of cooling air through the spiral openings 18 of the lattice section. The openings '18 have cross webs l9 connecting the horizontal ends of the diamonds, dividing the diamonds into pairs of triangles. As in the previously described constructions, the corners 80 at the horizontal ends are sharp since the load forces tend to squeeze these corners together and the intermediate corners 8| are rounded. Each half of the tire is made as a unit in a mold having pairs of triangular shaped helical cores spaced apart to form the diamond shaped openings 18 with the connecting cross web '19. The pitch of the spiral cores is such that each core extends from one side of the half tire to the other in one complete revolution. This results in elongated slits 82 (Fig. 7) on the side walls of the tire on opposite sides of the cross webs 19.

The dissymmetry of the slits 82 (Fig. 7) is due to extensions to provide side cushions. The first and third tiers of diamonds (counting from the tread) instead of terminating at surfaces 83 (Fig. 8) in the plane of the outside edge of the rim I l, have the center web projecting to form ribs 84 (Fig. 9). These ribs extend for 60 degrees in the plane of the rim edge, slope outward for 60 degrees as indicated at 85 (Fig. 7), slope back to the plane of the rim edge as indicated at 88 and then repeat the pattern. The second and fourth tiers of diamonds (counting inward from the tread) follow the same pattern: 60 degrees in the plane of the rim edge, 60 degrees sloping out from the plane of the rim edge as indicated at 81, 60 degrees sloping back to the plane of the rim edge as indicated at 88. In the case of the second and fourth tiers, the side walls 89 and 90 of the diamonds project beyond the plane of the rim edge providing tents" 98 enclosing the projecting web 78. This results in staggered V-shaped projections having peaks 91 and 92 as indicated in Fig. 10 forming buffers for the sides of the tire.

The cooling air enters through the openings on the outside of the tire on each side of the ribs 84 and in the tents 90a and travels along the openings to the space 11 between the rim sections 74. The cooling air slot 11 may be triangular as shown in Fig. 8 or of uniform width as shown in Fig. 9. From one aspect the circulation is due to the inertia of the outside air. The tire moves relative to the outside air and the differential between the inertia of the air and the friction drag on the walls of the openings 78 results in a heat transfer wiping action of the air against the walls of the openings 18.

The transmission of radial loads is the same as in the circumferential lattice tire. The load from the tread is transmitted from ribs 92a through inclined walls 9212 by shear to junctions 93. From junctions 93, the load is transmitted by shear through inclined walls 84 to junctions 95. This load transmitting pattern is repeated through each tier of the lattice. The walls 92b and 94 are proportioned to have equal load carrying capacity. As in the circumferential lattice tire the load is carried through the inclined walls, and is distributed between compression and shear in a ratio determined by the inclination of the walls. The cross webs 19 resist horizontal spreading of diamonds and thereby increase the stiffness or load carrying capacity of the inclined walls. From another aspect the cross webs 19 resist bulging of the side walls of the tire under radial load. Since the function of the cross webs 19 is to resist this bulging movement the cross webs may be formed of any flexible material and need not be rubber.

In the Figs. 7-10 construction of the tire is made in right and left halves with the spiral in one half opposite to the spiral in the other half. In the Fig. 11 construction where the center slot H is omitted, the lattice spirals in the same direction. If the pitch is the same as illustrated in Figs. 7-10 the cooling air makes two complete revolutions around the tire while passing from one side of the tire to the other. The tents 98a on one side of the tire face forward and serve as inlets for the air. The tents 98a on the opposite side of the tire face backward and have an ejector action aiding the circulation of the air. In Figs. 7-10 the tents 90a on both sides of the tire face forward and serve as inlets. In other respects, the construction and operation is the same as in the Figs. 7-10 tire.

In Figs. 12-17 is shown a helical lattice tire molded in two halves with the lattice sections spiralling from one side of the tire to the other. Each half of the tire has a tread section 96, a helical lattice section 91 and a rim section 98 bonded to the lattice section.

The tread section has circumferential grooves 89 with axially extending ribs I which hold the tread against radial shrinkage upon cooling. The ribs I80 project from opposite sides of the groove in staggered overlapping relation. From one aspect, the ribs I80 serve as undercuts. The lattice section has the diamonds I8 and cylindrical cross webs 18 of the Figs. 7-11 tire. Th diamonds and cross webs are formed by helical cores of triangular cross section. The cores spiral in the same direction in each half of the tire and when the halves are assembled, the openings formed by the cores are in register i-soi'there are continuous openings spiralling: from one side of the tire to thefo'ther. l'lhere are interlocking or z interfittingzprojections I I and I02 1 in the tread sections and; in i junctions I 03 in theL-lattice:sections. .Thesei locate and hold the engaging iacesaoi theitire. section ifrom radial 1 displacement. Z'Ihe .rim sections have tour-led edges 104 "which are clamped against the .wheel rlmiedges'zby throughl-bolts. I 05. 'iUpon'tightensingflof ithe through' ibolts, the curlediedges' are centered:ron' the"wheel rimsedges-andsiniefiect ithe tire "rims :are supported 1 on the 'wheel rim -by tension: forces exerted ioni theziinside .or .the :curledc-edges I04. :rhams the line of contact betweenithe:curledeedgesi and the" wheel: rim :is

: ini the-region: of I06 and this? givesz a wedging section on thelunderfside' of the edge of the stand- :ard adrop rim. I. Other methdds :of engagement r-may theadopted but the engagement with I the Rwheek rim is not limited to thisispeciflcarrange-:;

ment. The iorceiexerted on the' curled edg'es i'is in the direction lot I the aarrow I II]. Because citheztread: sectionchas ribs I08 which :are .parallel to ithe'rcenter 'line ofthe -tireg there is no need ltotmake '1 the tire haives in right land leftisec- :polnt; the" web section. 19: is .approachingia peak i I III, Bhaving started at point I I l in 5 the: plane *1Il9:.a'nd slopes. axially outward. In Ffig.-.16,'.the diamond 18 is half way into the tire sidewall and? the web 19 is 'fiusht withthe" tire side: wall. AtrFig. .17; the diamond which started-at point 3 H011 to. emerge from the sidewall 09 0f the tire reaches .-.a peak I I 2 and in eifect -provides a "tent; I I3 facing? in the direction of rotation-of --thetireat the inlet-side: and-servingas-a:guide ion-the. airren'tering' the diamondscla. At the discharge :side of the tire this' tentprovides 1 an 'ejcctor. force tothefiiseharget of:- air. From the -pe'ak'H2,'the.tent H31 and the web wislopes back toward the plane 'I oaand: reaches the-plane atgpoint III. -starts:to I emerge from the side walls of the tire :to the-peaks I I2, theuweb T19. continues at'a constant; projection andiprovides a buffer rib I l 4. rEach' of therzdiamonds l8 and webs 19: repeats -'-the same pattern.

Fig. 18 is a diagrammatic view showing one of r theidiamon'ds spiralling along. theaxis-of the tire. As i the .tire'frotates; elongated diamond shaped openings Ilsziunder the tents: I I3.:on oneside of the: tire: bite :intoithe stationary air and fill -the- 1 diamonds :18. :Except"forzfriction idrag -whic'h causes a wiping action-"against the inner surfaces Ofthe diamonds 18, the airfremains 2' stationary due to f its inertia and: the diamonds :spiral past the. air. ="Atthextdischarger' ends:oft'theropenings- H5 these tents haveanfejector effect. iIn other "'words, the 5 air" except: for the :friction I drag re- -mains relatively stationary; and. the wallstmove spirally over the engaging air. .E'AtIpoint oficontact with the "road, where r the tire ..is: relatively momentarily *stationary with the r-road at the :point of contact, the deflectionunder load results in'a 'fiattening ofthe diamonds indicated at 1. :This fiatteningsdoes not interfere=with the rela- =tivemovementhetween the-ainand-the :diamonds Fromv point HIM-where the tent a0 '15 c air to' exchange the air'irom one side to" the other.

'-This exchange takes place without a great'idisturbancein' the relative movement of the air alid walls inother parts of the 'passage except that induced by the frictionaldrag. "The wiping air is subjected to a turbulence=azid= passes from'the wallsurfaces readily to "the inner" areas-orthe passages as it is not materially disturbed through centrifugal action operating onthe air. Thus'its temperature is"more"nearly "maintained *and -a 'Igreatenproportion" of the volume of air' brought -into"h'eat exchange activity. This tu'rbulenceis accelerated attherestriction'at"the "road. "If "liquid orrsu'ch*matter enter" the'passage there- 'zstri'ction' assists ininfluen'cing adischarge.

" What I' claim asnew'is:

' lf In a" tirehaving' an outer tread and'an'in- 'terior cushion, the cushion having circumferentially directed walls intersecting to formralattice in section radially crosswise or the tire, the'walls 35 being spirally directed.

2. Inia tire'havingan' outer tread-and'andni' terior' cushion," the cushion having circumferentia'lly'directedwalls intersecting to form alattice 0 in section radially crosswise of the'tirei'the'wails spiralling to provide'passages through'the cushion 'for cooling air.

13.In a tire having an. outer treadandan interior cushion; the cushion' having'circumfer'en- .tia-llydirected walls intersecting to'form a lattice l insection radially crosswise-of the tire,'"the walls spiralling to provide passages through the cushion -for. cooling -air,. the-pitch ofthe'spiral being such as to. induce. relatively little? forward. movement of 'thelair. as compared to the forward movement of the walls.

- 4=Ina-tire having atread and-a-n intermediate cushion, the cushion. having circumferentially (extending walls .intersectingto form aclat'tice having nested-diamonds: in radial section: crosswise I of the tread,- =-and: other circumferentially extending walls- J'oining the sides ofthe .diamonds :and dividing thediamonds into triangles.

5.:In a tire havinga tread a rima-nd a-n inter- :mediate cushion f-ree toyield locally,- the cushion having walls intersecting to form a .--lattice of nested diamonds im section ina; plane: radial: to the tread, and walls extending across: theadiaemonds and 'dividing thexdiamonds in-to upper'and rlower: triangles.

#6.. In a tirehavingatread a rim, and'an inter- ?mediatecushion tree to-yielcl locally, the cushions having-sectionssspaced apart-axially to provide-a center slot between the sections,--and each section 59- having circumferentially. extending walls forming passages spiralling. from theucenter slot' toward the-outsideof the. tire,- the pitch a of. the spiral in one section-being opposite "to i the a pitch of .the

spiral in: the (other 1 section.

'7. :In=a tire having'a tread a rim; andan-intermediatecushionfree to yield-locally,- thercushion having: clrcumferentially:extending walls inter- -secting to 'forma- :lattice having-nestedsdiamonds in radial sectioncrosswise oi. the .treadg-andother "circumferentially vex-tending walls joining -.-the sides of the diamondsand dividing .the diamonds into upper and. lowertriangles, thewalls spiralling from one side'of the treadto the othenand :said :first and-other. circumferentiallyextending walls:alternatelyspiralling beyond the side. of, the

cushion to provide respectively air receiving passageways and side cushion ribs.

8. In a tire, a tread, and a load carrying cushion for the tread having circumferentially extending helical walls intersecting to form angular openings with apexes extending radially, the walls spiralling axially from one side of the tread to the other.

9. In a tire, a tread, a load carrying cushion for the tread, circumferential air cooling openings in the cushion spiralling around the tread, and Walls on the side of the cushion defining tents projecting into the air and aiding the flow of air through the openings.

10. In a tire having an outer tread, and an interior cushion free to yield locally, the cushion having circumferentially extending walls intersecting to form a lattice in radial section crosswise of the tread, the walls spiralling axially of the tire and, the tread having spiral road contacting ribs conforming with the spiral of the lattice walls.

HUGH C. LORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 485,633 Keating Nov. 8, 1892 819,036 Ashley May 1, 1906 912,943 Duff Feb. 16, 1909 982,634 Reed Jan. 24, 1911 1,494,797 Nimschke May 20, 1924 1,557,324 Pestunowitz Oct. 13, 1925 1,662,007 Kuhlke Mar. 6, 1928 1,685,955 Overman Oct. 2, 1928 1,841,773 Worsley et al Jan. 19, 1932 2,048,635 Kraft July 21, 1936 2,108,406 Kraft Feb. 15, 1938 2,150,107 Shields Mar. '7, 1939 FOREIGN PATENTS Number Country Date 489,359 Great Britain 1938 647,230 Germany Oct. 16, 1934 

